1. Field of the Invention
The present invention relates to a method for detecting injection performance in fuel injecting operation of a fuel injection valve, and more particularly to a method for detecting injection timing, the amount of injection and the fuel injection rate in a fuel injection valve for internal combustion engines.
2. Description of the Prior Art
Up to now there has been widely used a fuel injection valve provided with a nozzle needle and a pressure spring for biasing the nozzle needle toward the associated valve seat, and as soon as pressure exerted by the supply of the pressurized fuel exceeds the tension of the pressure spring, pressure acting on the pressure taper of the nozzle needle causes the nozzle needle to be lifted off the valve seat and fuel is injected from the injection hole or holes into the combustion chamber. For detecting the fuel injection performance of the fuel injection valve of the type described above, Japanese Utility Model Application Public Disclosure No. Sho 61-144267 discloses a detecting system in which a piezoelectric element is provided for detecting changes in the tension of the pressure spring and the time at which the the fuel injection starts is detected on the basis of the level of the output voltage developed across the opposite surfaces of the piezoelectric element.
However, since the proposed detection system is directed to detection of only the time at which injection of fuel begins on the basis of change in the level of the voltage signal representing the force produced in the pressure spring at the beginning of fuel injection, it is impossible for the proposed detection system to detect fuel injection parameters other than the time at which injection of fuel begins, and specifically for it to detect the fuel injection rate, the amount of fuel injected and the like.